In recent years natural gas has progressively increased in importance and has become a primary heating fuel that continues to gain in prominence in the transportation industry and, to a less extent, for fueling automobiles and busses. This has caused natural gas to increase in cost and become important as fuel. Therefore, there is a need for accurate measurement for sales purposes domestically as well as in other areas of the world.
Natural gas is produced from drilled oil wells and gas wells. The gas production formations are located deep within the earth in huge caverns or sometimes in solution in an oil reservoir. The gas is produced from a wellhead located at the earth's surface, and it is measured by a metering device or meter run as it flows into a pipeline where it is transported into a gas processing plant and is cleaned and processed, with the residue being distributed to the user market as sales gas.
During the above events, the gas is measured at various places to insure accurate sales data. This is achieved by a meter run having a charting instrument that shows the amount of flow for any given time period. Hence, the gas usually is measured many times as it flows from the wellhead to the user market.
There is always a possibility that gas will back-flow in a downstream direction and travel back through the metering device due to reversal of gas pressure for one reason or another. After this problem has been remedied, the gas resumes flow and often it is measured by the metering device a second time, causing someone to pay twice for the same volume of gas.
This problem is remedied by a check valve apparatus that is placed at the immediate downstream side of the meter run, in accordance with the present invention.